Thermal ink-jet printers provide an effective means of propelling ink-jet inks onto various media including paper. These printers can accomplish this by using resistive heater elements for heating the ink to a boil, and propelling the ink through an overlying orifice plate. Specifically, a typical ink-jet printhead has an array of precisely formed nozzles located on a nozzle plate and attached to an ink-jet printhead substrate. The substrate incorporates an array of firing chambers that receive liquid ink (colorants dissolved or dispersed in a solvent) through fluid communication with one or more ink reservoirs. Each chamber has a thin-film resistor located opposite the nozzle so ink can collect between the firing resistor and the nozzle. Upon energizing a particular resistor element, a droplet of ink is expelled through the nozzle toward a print medium. Such printers, as typified by the Hewlett-Packard DeskJet™ and DesignJet™ printers, are desirable for use for several reasons. For example, thermal ink-jet printers have a relatively fast throughput while being relatively inexpensive to run. Additionally, these printers are relatively easy to use, and the ink is easily replaced.
There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly paper and coated media. Some of these reasons include low printer noise, capability of high-speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, though there has been great improvement in ink-jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, new applications, etc. As new ink-jet inks are developed, there are several traditional characteristics to consider when evaluating the ink in conjunction with a printing surface or substrate. Such characteristics include edge acuity and optical density of the image on the surface, dry time of the ink on the substrate, adhesion to the substrate, lack of deviation of ink droplets, presence of all dots, resistance of the ink after drying to water and other solvents, long-term storage stability, good dot size and dot gain, color-to-color bleed alleviation, less chia, acceptable coalescence, and long term reliability without corrosion or nozzle clogging. Though the above list of characteristics provides a worthy goal to achieve, there are difficulties associated with satisfying all of the above characteristics. Often, the inclusion of an ink component meant to satisfy one of the above characteristics can prevent another characteristic from being met. Thus, most commercial inks for use in ink-jet printers represent a compromise in an attempt to achieve at least an adequate response in meeting all of the above listed requirements.
In general, ink-jet inks are either dye- or pigment-based inks. Dye-based ink-jet inks can use a soluble colorant that is usually water-based to turn the media a specific color. Insoluble dyes have also been used in ink-jet ink formulations, wherein the insoluble dyes are dispersed rather than solubilized in a liquid vehicle. Such insoluble dyes can be considered to be similar to pigmented inks, which typically disperse the colorant within the liquid vehicle. In many cases, the line quality and accuracy of plots produced by insoluble colorant-based inks can be superior to that of water-soluble colorant-based inks. However, color saturation is often superior with water-soluble dye-based ink-jet inks.
As water soluble dye-based ink-jet inks have been shown to provide good color saturation, and as technology has evolved where line quality and accuracy of plots for dye-based ink-jet inks has improved, there has been increased interest in using water-soluble dye-based ink-jet inks. As such, it would be an advancement in the art to provide water-soluble dye-based ink-jet inks that are versatile, performing well under a variety of conditions.